The free solution conformation of peptides serves as a logical starting point for delineating their conformation-activity relationship. We propose to determine the conformation of angiotensin II in aqueous solution by means of intramolecular and intermolecular nuclear Overhauser effect (NOE) measurements, by NMR experiments involving binding of paramagnetic lanthanide ions, and by fluorescence measurements. Specifically, it is proposed 1) to apply a method for quantitative measurement of NH proton exchange rates by solvent saturation experiments in using a combination of Fourier transform and correlation NMR spectroscopy, 2) to make quantitative or semiquantitative estimation of the exposure to solvent of CH protons by intermolecular NOE experiments in H2O, 3) to analyze the intramolecular data for angiotensin II and the paramagnetic shift and relaxation data in terms of models proposed for this molecule. Fluorescence experiments will be conducted to 1) measure the pH profile of metal binding using Tb 3 ion and 2) quantitate the extent of solvent exposure of the tyrosine side chain of angiotensin II using quenching experiments.